Drinking Water Frequently Asked Questions (FAQs) | Drinking Water | Healthy Water | CDC

Get answers to frequently asked questions about public and private water systems.

Water Sources

Where does my drinking water come from?

The United States has one of the safest and most reliable drinking water systems in the world. Every year, millions of people living in the United States get their tap water from a public community water system.

The drinking water that is supplied to our homes comes from either a surface water or ground water source. Surface water collects in streams, rivers, lakes, and reservoirs. Ground water is water located below the ground where it collects in pores and spaces within rocks and in underground aquifers. We get ground water by drilling wells and pumping it to the surface.

Water travels to your tap from a surface water or ground water source through your local water utility or through an individual water system, such as a private well.

A private well uses ground water as its water source. Owners of private wells and other individual water systems are responsible for ensuring that their water is safe from contaminants.

 Top of Page

Public Water Systems

Water Quality

How is my drinking water regulated?

All public water systems in the United States are required to follow the standards and regulations set by the U. S. Environmental Protection Agency (EPA). EPA regulations that protect public water systems do not apply to privately owned wells or other individual water systems. Owners of private wells are responsible for ensuring that their well water is safe from contaminants.

What type of health issues can be related to water quality?

Contaminants in our water can lead to health issues, including gastrointestinal illness, reproductive problems, and neurological disorders. Infants, young children, pregnant women, the elderly, and people with weakened immune systems may be at increased risk for becoming sick after drinking contaminated water. For example, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Federal law requires that systems reduce certain contaminants to set levels in order to protect human health.

How do I know that the water in my home is safe to drink?

EPA is responsible for making sure that public water supplies within the United States are safe. In 1974, Congress passed the Safe Drinking Water Act. This law sought to protect the nation’s public drinking water supply by giving EPA authority to set the standards for drinking water quality and oversee the states, localities, and water suppliers who implement those standards. In 1986 and 1996, the law was amended to protect drinking water and its sources, which include rivers, lakes, reservoirs, springs, and ground water wells.

How do germs and chemicals get into my drinking water?

There can be many sources of contamination of our water systems. The most common sources of contaminants include:

• Naturally occurring chemicals and minerals (e.g., arsenic, radon, uranium)
• Local land use practices (e.g., fertilizers, pesticides, livestock, concentrated animal feeding operations)
• Manufacturing processes
• Sewer overflows
• Malfunctioning wastewater treatment systems (e.g., nearby septic systems)

EPA regulates many contaminants that pose known human health risks. EPA makes sure that water meets certain standards, so you can be sure that high levels of contaminants are not in your water.

How do I filter water at my home if I am concerned about water quality?

Different water filters have different functions. Some can make your water taste better, while others can remove harmful chemicals or germs. Visit CDC’s filter page to learn more about home water filters.

How do I remove the parasite Cryptosporidium from my drinking water?

The parasite Cryptosporidium can survive a long time, even after the water is treated with chlorine or iodine. Cryptosporidium can be removed from water by filtering through a reverse osmosis filter, an “absolute one micron” filter, or a filter certified to remove Cryptosporidium under NSF International Standard #53 for either “cyst removal” or “cyst reduction.”  Filtering does not remove bacteria and viruses. Ultraviolet light treatment of water is not effective against Cryptosporidium at normally used levels.

How can I find out if there has been a violation in our public water standard?

When water quality standards have not been met, your public water system must alert and notify customers if there is a risk to their health. Your annual Consumer Confidence Report (CCR) is another way to find out about the water quality in your area, and find information regarding contaminants, possible health effects, and the water’s source.

 Top of Page

Water Testing

Who do I need to contact to find out more information about water quality in my area?

Every community water supplier must provide an annual report to its customers,  known as a Consumer Confidence Report (CCR). The report provides information on your local drinking water quality, including the water’s source, contaminants found in the water, and how consumers can get involved in protecting drinking water. Visit EPA’s website to find your local CCR.

How often does the local public water system test my drinking water?

Frequency of drinking water testing depends on the number of people served, the type of water source, and types of contaminants. Certain contaminants are tested more frequently than others, as established by the Safe Drinking Water Act. You can find out about levels of regulated contaminants in your treated water for the previous calendar year in your annual Consumer Confidence Report (CCR).

What common contaminants are included in this testing?

EPA sets standards and regulations for the presence and amount of over 90 different contaminants in public drinking water, including E.coli, Salmonella, and Cryptosporidium species. Visit EPA’s Drinking Water Contaminant Candidate List and Regulatory Determination website for more information.

What should I do if I want my household water tested?

The United States has one of the safest public water supplies in the world. However, if you are concerned about contaminants in your home’s water system, contact your state drinking water certification officer to obtain a list of certified laboratories in your state. Depending on how many contaminants you wish to test for, the cost of a water test can range from $15 to hundreds of dollars. Visit EPA’s Safe Drinking Water Information website if you have questions on testing methods.

Who should I contact if my water has a funny smell, taste, or appearance?

A change in your water’s taste, color, or smell is not necessarily a health concern. However, sometimes a change can be a sign of problems. If you notice a change in your water, call your public water system company.

If you want to test your water, your local health department should assist in explaining any tests that you need for various contaminants. If your local health department is not able to help, contact a state certified laboratory to perform the test. To find a state certified laboratory in your area, call the Safe Drinking Water Hotline at (800) 426-4791 or visit the State Certified Drinking Water Laboratories list.

 Top of Page

Water Advisories

How do I find out if there is a boil water advisory or other water advisory in my community?

Your public water system is responsible for notifying residents if the water quality does not meet EPA or state standards, or if there is a waterborne disease emergency. EPA sets guidelines for when residents must be notified depending on the seriousness of a contamination event. You should be notified by media outlets such as TV or radio, mail, or other communication channels. There are three levels of public notification:

• Tier 1 is for the most serious and acute contamination events. Notification must be broadcast by local media within 24 hours.
• Tier 2 allows for a 30-day notification.
• Tier 3 provides notification through the annual Consumer Confidence Report (CCR).

If there is a boil water advisory in my community, how do I disinfect my drinking water?

To disinfect your drinking water during a boil water advisory, you should boil your water at a rolling boil for at least 1 minute (at elevations above 6,500 feet, boil water for 3 minutes). Boiling your water for at least 1 minute at a rolling boil will kill all harmful bacteria, parasites, and viruses from drinking water. You can also treat small volumes of drinking water by using a chemical disinfectant, such as unscented household chlorine bleach or by using a water filter. Visit CDC’s make water safe page for more information.

 Top of Page

Private Wells

What are the main types of ground water wells?

According to EPA, there are three basic types of private drinking wells: dug, drilled, and driven. Proper well construction and continued maintenance are critical to the safety of your water supply. It is important to know what type of well you have. Well type affects how likely your water is to become contaminated and what kind of maintenance procedures you should follow. You may be able to determine the type of well you have by looking at the outer casing and cover of the well.

As a private well owner, should I have my well tested?

Yes, as a private well owner, you are responsible for testing your well to ensure the water is safe to drink. EPA is responsible for making sure that the public water supply within the United States is safe. However, EPA does not monitor or treat private well drinking water. For information on testing your well water, visit Drinking Water’s Well Testing page.

What germs and chemicals should I test for in my well?

Several water quality indicators (WQIs) and contaminants that should be tested for in your water are listed below. A WQI test is a test that measures the presence and amount of certain germs in water. In most cases, WQIs do not cause sickness; however, they are easy to test for and their presence may indicate the presence of sewage and other disease-causing germs from human and/or animal feces (poop). For more information on these contaminants and WQIs, please see the Drinking Water’s Well Testing page.

Water Quality Indicators:

• Total Coliforms
• Fecal Coliforms / Escherichia coli (E. coli)
• pH

Contaminants:

• Nitrate
• Volatile Organic Compounds (VOCs)

Other germs or harmful chemicals that you should test for will depend on where your well is located on your property, which state you live in, and whether you live in an urban or rural area. These tests could include testing for lead, arsenic, mercury, radium, atrazine, and other pesticides. You should check with your local health or environmental department to find out if any of these contaminants are a problem in your region.

Please remember that if your test results say there are germs or chemicals in your water, you should contact your local health or environmental department for help in interpreting the test, ask for guidance on how to respond to the contamination, and test your water more often.

When should I have my well tested?

You should have your well tested once a year for total coliform bacteria, nitrates, total dissolved solids, and pH levels. If you suspect other contaminants, you should test for those as well. However, spend time identifying potential problems first, as these tests can be expensive. You should also have your well tested if:

• There are known problems with well water in your area.
• You have experienced problems near your well (e.g., flooding, land disturbances, and nearby waste disposal sites).
• You replace or repair any part of your well system.
• You notice a change in water quality (e.g., taste, color, odor).

Who should test my well?

State and local health or environmental departments often test for nitrates, total coliforms, fecal coliforms, volatile organic compounds, and pH. Health or environmental departments, or county governments should also have a list of the state-certified (licensed) laboratories in your area that test for a variety of Water Quality Indicators (WQIs) and contaminants. For more information, visit EPA’s pages below or contact your local health department:

My well water has a funny smell or taste; should I worry about getting sick?

Any time you notice a significant change in your water quality, you should have it tested. A change in your water’s taste, color, or smell is not necessarily a health concern. However, sometimes changes can be a sign of problems.

How do germs and chemicals get into my well water?

A private well uses ground water as its water source. There are many sources of contamination of ground water. Some of the most common sources of contaminants include:

• Naturally occurring chemicals and minerals (e.g., arsenic, radon, uranium)
• Local land use practices (e.g., fertilizers, pesticides, livestock, animal feeding operations, biosolids application)
• Manufacturing processes
• Sewer overflows
• Malfunctioning wastewater treatment systems (e.g., nearby septic systems)